1. Field of the Invention
The present invention relates to the field of binder and film-forming or gel-forming compositions, particularly towards substitutes for gelatin, and particularly for non-gelatin capsules for oral delivery of medications or diet supplements. Non-oral systems include cosmetics, bath additives, and the like.
2. Background of the Invention
Gelatin has found a wide range of commercial utility, and within certain industries is essentially irreplaceable. It has been used in wet processed photographic emulsions for more than a hundred years, it has been used to deliver pharmaceuticals in capsule form for more than one hundred years, it is used in cosmetics as a binder, and is regularly used in a wide range of food products, such as gelatin containing courses, compressed meats, pastries. It has many useful physical and chemical properties which support this broad range of utility.
Gelatin is manufactured by the hydrolysis of animal by-products which contain collagen. This is usually found in animal bones, animal skins and white animal connective tissue. The collagen containing material is boiled in water, leaving behind the colorless or pale yellow protein which constitutes the hydrophilic colloid material of the gelatin.
The primary sources of gelatin are from bovine animals and pigs, although fish and birds have been indicated in the literature as alternative, small volume sources of gelatin. The source of gelatin can be a problem for potential areas of use or for particular consumers. Large groups around the world cannot ingest any products of pigs (e.g., vegetarians, the Hebrews and the Muslims) or the products of beef (the Hindus and vegetarians). As medication and/or diet supplements are provided in gelatin capsules without any indication of the source of the gelatin, the use of capsules is restricted in areas where religious beliefs would need to question the source of the gelatin. Additionally, as there has recently been at least one alleged instance of cross-species contamination from cattle to humans (at least one alleged instance with bovine spongiform encephalopathy, BSE, or "Mad Cow Disease" in the United Kingdom), the use of uncontrolled by-products from animals has lost some level of commercial acceptance. It has become apparent that replacement compositions for gelatin which are not derived from animals are desirable.
Carrageenan is a natural hydrocolloid, a polysaccharide hydrocolloid, which is derived from seaweed. It comprises a carbohydrate polymer of repeating sugar units, which is linear, without significant numbers of branches or substitutions. Most, if not all, of the galactose units on a Carrageenan molecule possess a sulfate ester group. The exact position of the sulfate groups, the cations on the sulfate groups, and the possible presence of an anhydrous bridge on the molecule differentiates the various types of Carrageenan. There are basically three distinct types of Carrageenan which each behave differently and have distinct properties and differences. These are the kappa, iota and lambda forms of Carrageenan, although there are also minor fractions of mu and nu Carrageenan forms. These various forms can significantly vary in properties, as exemplified by the fact that lambda Carrageenan in solution is unable to associate into a structure, so that it cannot gel, but may act as a thickener. Both kappa and iota Carrageenan are able to gel. Kappa Carrageenan is known to form gels in the presence of potassium cations. These gels tend to be brittle and exhibit syneresis (contraction and release of entrapped liquid) as the gel shrinks. Iota Carrageenan tends to react strongly to calcium cations and forms a more tender, flexible gel than kappa Carrageenan that is not as susceptible to syneresis.
U.S. Pat. No. 3,962,482 describes clear, elastic, water gels and gel-forming compositions that are based on potassium-sensitive carrageenan in the form of an alkali metal or an ammonium salt and a water-soluble potassium salt. Addition to the composition of calcium-sensitive carrageenan, also in the form of an alkali metal or an ammonium salt, imparts freedom from syneresis. The water gels and the gel-forming compositions are characterized by essentially complete freedom from polyvalent metal cations. The invention is particularly concerned with the formation of compositions for use with edible dessert gels.
U.S. Pat. No. 5,089,307 discloses heat-sealable, edible films comprising at least a film layer containing a water-soluble polysaccharide as the principal component, or comprising at least (a) a film layer as described above and (b) a subfilm layer containing an alkali metal salt of casein, soybean protein or a combination of soybean protein and gelatin, as the principal component. Preferably, the water-soluble polysaccharide is composed chiefly of carrageenan and the film layer additionally contains a polyhydric alcohol. These edible films are useful in sealing or packaging powdery foods, granular foods, dry solid foods, oily foods and the like.
U.S. Pat. No. 5,002,934 describes aqueous gels, gel-forming compositions and composites containing the same, comprising carrageenan and a cation of such a type and in such a concentration that the gel has a transition midpoint temperature below 45.degree. C. and a yield stress of at least 0.5 kN/m.sup.2 at 5.degree. C. The gels or gel-forming compositions can advantageously be used in food and toiletry products.
U.S. Pat. No. 4,276,320 describes a method and a kappa carrageenan composition for making a water dessert gel having a controlled melting temperature so as to soften or melt within the mouth of the consumer and providing for excellent flavor release, good mouth feel and containing only kappa carrageenan, and sodium salt of a sequestering agent with ionizable potassium in amounts sufficient to sequester all polyvalent cations present.
U.S. Pat. No. 3,956,173 describes cold water gellable compositions that are prepared based on the sodium salt of kappa-carrageenan and a potassium salt. Gelation is controlled so that good quality gels result by encapsulating the potassium salt in a water-soluble hydroxypropyl cellulose.
Each of these various systems has particular needs due to the specific types of use to which the Carrageenan compositions are put. There is no specific disclosure within these references as to the parameters and modifications in the compositions and processes which would make Carrageenan compositions more suitable for use in thermally sealed, orally administered gelatin-like capsules.